The present invention concerns a laser operation device having a hand piece provided with a probe to be inserted into an irradiated region and, more particularly, it relates to a laser operation device which is most suitable as an intraocular operation device for cataract, glaucoma or the like, and in which a fiber portion is not in contact with intraocular tissue even when a top end that emits a laser beam is destroyed by laser energy or the like and, further, a connection portion of the fiber is less damaged by the laser energy.
For a patient suffering from lens opacity caused by cataract, no effective therapeutical agent is known at present for making the lens transparent, so that an operation for extirpation of a clouded lens is necessary for the recovery of impaired vision.
As an operation method for cataract, an ultrasonic emulsifying and sucking method has generally been put to practical use in recent years. Although there has been a limit on the ultrasonic emulsifying and sucking method in that this is effective only to a soft lenticula, a lenticula dividing method has been proposed and the ultrasonic emulsifying and sucking method has now been applied also to a hardened lenticula.
That is, in the lenticula dividing method, a predetermined amount of perfusate is injected between each laminar layer of the lenticula to separate layers from each other thereby softening the lenticula. In the ultrasonic emulsifying and sucking method, an ultrasonic wave at about 27 to 55 KHz is applied to cause vibrations under injection of the perfusate, which induces cavitation and destroys a lens tissue suffering from cataract by the mechanical destroying action thereof, and then emulsified lenticula tissue and the perfusate are sucked.
For a relatively soft lenticula, a lens capsule is at first incised and then a cataract lens tissue is destroyed and sucked by an ultrasonic emulsifying and sucking method. Then, an operation for inserting an artificial lens into the remaining lens capsule is conducted. For incising the lens capsule, a circular incising method is generally used, because the method provides a symmetrical opening, causes less cracking to the periphery of the lens capsule and results in less troubles to eye tissues. Further, since the inserted artificial lens can be kept stably, that possibility of vision impairment caused by axial displacement of the artificial lens after the operation is reduced.
For a lenticula hardened considerably upon further progress of cataract, neither incision of the lens capsule nor the ultrasonic emulsifying and sucking method is applicable but a whole extirpation of removing all the lens capsule is conducted. However, since the intracapsular extirpation leaves no lens capsule, the artificial lens can not be stably fixed in the eye. Accordingly, hydrodelineation is applied by oscillating a top end of a fine wire by ultrasonic waves, injecting perfusion of a balanced salt solution from the top end to defoliate the layers of the lens capsule from each other.
A hand piece using a laser beam has been developed for removing lens tissue in an eye suffering from cataract. The hand piece comprises a hand piece main body, means for transmitting a laser beam at a wave length corresponding to an absorption peak of water, a perfusing means for perfusing a perfusate and a sucking means for sucking tissue evaporated by the laser beam.
The hand piece is provided with a probe for a laser scalpel and the probe uses, for example, ZnSe crystals as a support member for the fiber for protecting an emitting end face of the fiber.
Further, there is a fiber having an outer diameter equal to or greater than that of a laser beam power transmission fiber and attached to the top end of the probe for protecting the end face of the power transmission fiber and focusing or diverging the emitted laser beam.
However, the probe used in the conventional hand piece as described above is inefficient because the shape of a protecting member for the top end of the fiber attached to the top end of the probe is complicated. The protection member for the top end of the fiber has to be fabricated at a high accuracy in order to improve the sealing effect at the top end of the fiber, making it difficult to reduce the diameter of the probe.
When conducting an accurate intraocular operation using the laser probe, it is necessary to reduce the beam diameter of the irradiating laser beam by minimizing the core diameter at the top end. However, since the laser beam irradiated from the top end of the optical fiber diverges from the entire surface of the core at an angle defined by the number of aperture of the fiber, even if the top end of the fiber is fabricated into a convex lens shape or a convex lens is disposed to the top end, it is difficult to focus the irradiating laser beam to smaller than the core diameter of the fiber.
Further, since the support member for the fiber is constituted, for example, with crystals of ZnSe or the like, it can not be said non-toxic to a human body and it is not suitable as a fiber end probe to be inserted into the human body.
Further, for the hand piece using a laser beam, an infrared laser beam at a wavelength of about 2.9 .mu.m can be used but, since the infrared laser at a wavelength of about 2.9 .mu.m coincides with a sharp absorption spectrum of --OH group, it involves a problem that transmission, for example, through quartz fiber containing --OH groups in the ingredient is impossible.
Then, as a fiber capable of transmitting a sufficient energy of 2 J/cm.sup.2 (energy on the acting surface in an infrared laser beam at a wavelength of about 2.9 .mu.m) to act on a living body as a laser scalpel, a fiber mainly composed of zirconium type fluoride glass is considered most optimum at present. However, since the zirconium type fluoride glass fiber dissolves, although little, into water to form a fluoride, it involves a problem that it can not be inserted with no coverage into a human body.
Further, for introducing an infrared laser beam at a wavelength of about 2.9 .mu.m to an irradiation region, when a zirconium type fluoride glass fiber is used for a portion of the fiber, there may be a worry that the connection portion between the fiber and the top end is destroyed by the heat energy of the laser beam at the top end, as well as the possibility that the fiber portion, if it should be destroyed, is in contact with a living body tissue, so that it can not always be considered harmless to the human body.
Dehydrated epoxy type adhesives used for a laser scalpel or the like have properties wherein the molecular weight of the epoxy as a main agent is from 200,000 to 300,000, the molecular weight of the amine as a hardening agent is from 20,000 to 30,000 and a viscosity at an initial mixing stage is from 5 to 7 Pa.S (5,000-7,000 cP). For instance, it is 2-Hr hardened type Devcon 2-Ton Epoxy. Usual epoxy resins mainly comprise amine and epoxy of large molecular weight and, in addition, they also contain various amine and epoxy components of small molecular weight. If the epoxy resin is used as it is for the bonding of the zirconium type fluoride glass fiber, a chemical reaction occurs between the amine and the epoxy components of small molecular weight and the zirconium type fluoride glass fiber till the epoxy becomes hardened, thereby reducing the durability of the zirconium type fluoride glass fiber against laser energy.
Further, if epoxy resin is used as the adhesive, the connection portion of the first fiber portion tends to be destroyed by the heat energy of the laser beam prior to the second fiber portion formed to the top end, so that there may be considered such a problem that expensive zirconium type fluoride glass fibers have to be replaced frequently.
In addition, infection of virus or the like has caused a problem in recent years and it has now become a common practice to use a disposable probe to be inserted into a living body but there is a problem that it is impossible to make only the top end of the probe disposable in the conventional system.
Accordingly, it has been keenly demanded for the advent of a technique capable of accurately and easily positioning a core of a first fiber having a core diameter of less than 260 .mu.m and a core of a second fiber at a top end portion, adaptable to a disposable method of using the top end portion and for connecting the first fiber portion and the second fiber portion with excellent durability.